A new superterran exoplanet (aka Super-Earth),a rock-water world, was found in the stellar habitable zone of the red dwarf star Gliese 163 by the European HARPS team. The planet, Gliese 163c, has a minimum mass of 6.9 Earth masses and takes nearly 26 days to orbit its star. Superterrans are those exoplanets between two and ten Earth masses, which are more likely composed of rock and water.

Gliese 163 is a nearby red dwarf star 50 light years away in the Dorado constellation. Another larger planet, Gliese 163b, was also found to orbit the star much closer with a nine days period. An additional third, but unconfirmed planet, might be orbiting the star much farther away.

Gliese 163c could have a size between 1.8 to 2.4 Earth radii, depending if it is composed mostly of rock or water, respectively. It receives on average 40% more light from its parent star than Earth from the Sun, making it hotter. In comparison, Venus receives 90% more light from the Sun than Earth. We do not know the properties of the atmosphere of Gliese 163c but, if we assume that it is a scaled up version of Earth's atmosphere, then its surface temperature might be around 60°C. Most complex life on Earth (plants, animals, and even humans) are not able to survive at temperatures above 50°C, however, plenty of extremophilic microbial life forms can thrive at those temperatures or higher.

The detection of potential habitable exoplanets is pacing up. There are now six including the debated Gliese 581g, most of them detected just in the last year. Four of these bodies, Gliese 581d, Gliese 667Cc, Gliese 581g, and now Gliese 163c are around red dwarfs stars (M-star). HD 85512 is around a K-star (a middle star between the smaller red dwarfs and the Sun). Only Kepler-22b is around a Sun-like star (G-star). All of these planets are bigger than Earth but still considered potentially habitable, at least to simple life forms.

Scientists are trying to construct better ground and space observatories in the next decades to be able to detect smaller worlds, those more resembling Earth. The Habitable Exoplanet Catalog of the Planetary Habitability Laboratory @ UPR Arecibo (phl.upr.edu), which was not involved in the discovery, now includes and ranks Gliese 163c as number five in its main list of best objects of interest for life. Enlarge Current six potential habitable exoplanets ranked by similarity with Earth (Earth = 1.00). Four of these objects have been detected in the last year, from September 2011 to today.

The potential for habitable planets around red dwarf stars has been and issue of much debate. Tidal effects on the planets around these stars might cause extra surface heating or even tidal locking (always giving the same face to its parent star). Also, these stars are more active and their stellar wind might erode planetary atmospheres much faster. These factors might preclude the potential for life on smaller planets but not for planets with thicker atmospheres, something expected for superterran planets.

Our Solar System lacks an example of a superterran. Its eight planets are either the smaller terrestrial kind, like Earth, or the larger gas giants, like Jupiter. Understanding superterrans around red dwarf stars, a non Sun-like star, just adds to the challenge of assessing their habitability.

The NASA Kepler Mission has detected about 27 potential habitable exoplanets candidates out of their over 2,300 exoplanets that are waiting to be confirmed. Some of these bodies seem very Earth-like. Unfortunately, they are much farther away from us than Gliese 163 and it will be nearly impossible to determine if they are really habitable worlds by future observations.

However, the statistical analysis of Kepler suggests that these planets are very common in the galaxy. Therefore, many more Earth-like worlds are waiting to be discovered in our solar neighborhood too, such as Gliese 163c. The new exoplanets around Gliese 163 were discovered by the European HARPS team leaded by Xavier Bonfils from the UJF-Grenoble/CNRS-INSU, Institut de Plane ́tologie et d'Astrophysique of Grenoble, France.

Other participating scientists are from France, Germany, Portugal, Switzerland, and Belgium. Gliese 163c was announced by team member Thierry Forveille from the Observatoire de Grenoble during the International Astronomical Union session Formation, Detection, and Characterization of Extrasolar Habitable Planets from August 27th to 31st, 2012 in Beijing, China.

The inner edge of the habitable zone in our solar system, as most commonly defined, lies at 0.95 Au (the outer edge at 1.37 AU, for 1 atmosphere, or 1.67 AU for a 2 atmosphere super Earth).

If, our sun was 140 percent more luminous, then the inner edge of the habitable zone would be further out at 1.24 AU (sqrt 1.4) and Gliese 163 c would be then at the equivalent, in our solar system, of 0.84 AU. So Gliese 163 c at 0.84 AU is way inside the inner edge of the commonly understood boundaries of a habitable zone!

And, that's not even taking into account the fact that red dwarfs produce far more infra red light, as a percentage of their total luminosity, compared to the amount of infra red light our yellow dwarf sun does. It takes fewer watts of infra red light to heat up water than it takes for visible light. And so again, the inner edge of the habitable zone would be pushed further out by 10 more percent, at least, for Gliese 163. That would translate to 1.045 AU as the inner edge of the habitable in our solar system, as scaled up from Gliese 163. 0.84 Au would then be the equivalent of 0.76 AU in our solar system, so Gliese 163 c more or less orbits where sweltering Venus does.

But, that's not still not taking into account the fact that Gliese 163 c is a super Earth! A planet most likely starting with a much thicker atmosphere and larger water oceans. If the oceans of a super Earth were to evaporate away, as would happen at 60 Celsius, the atmosphere would end up becoming even thicker than Venus's 92 atmospheres, with much more nitrogen and far more carbon dioxide to heat up the planet, hundreds or maybe thousands of atmospheres. The temperature on Gliese 163 c's surface would then average at least 600 Celsius, hardly habitable!

All the misanthropes & Anti-Humanists: Do the Species a favour and end it all now. Else, get a life.

Jimbo, WTF? What are you smoking?

Icon Rant Tugh, cute nome de plume. I don't get what's going on with your maths. Insolation that's 40% higher is equivalent to 1/sqrt(1.4)= 0.845 AU. With ~50% cloud cover the inner edge of the Habitable Zone is at 0.76 AU, so Gliese 163c should be fine. It's likely to be a "Wet Greenhouse" but it's probably massive enough to hang-on to hydrogen and stay wet.

Maybe we should stop wasting time and resources looking outward and look inward for what needs fixxed... Earth can use some help!
If we used the billions we use on spacecraft on recycling programs we wouldnt need to search for new homes... simple logic to me.